Average Selling Price

Task: Find the average selling price for each product. average_price = total_price / total_units.

Table: Prices

+-------------+------+
| Column Name | Type |
+-------------+------+
| product_id  | INT  |
| start_date  | date |
| end_date    | date |
| price       | INT  |
+-------------+------+

Table: UnitsSold

+---------------+------+
| Column Name   | Type |
+---------------+------+
| product_id    | INT  |
| purchase_date | date |
| units         | INT  |
+---------------+------+

Input: Prices table:

+------------+------------+------------+-------+
| product_id | start_date | end_date   | price |
+------------+------------+------------+-------+
| 1          | 2019-02-17 | 2019-02-28 | 5     |
| 1          | 2019-03-01 | 2019-03-22 | 20    |
| 2          | 2019-02-01 | 2019-02-20 | 15    |
| 2          | 2019-02-21 | 2019-03-31 | 30    |
+------------+------------+------------+-------+

UnitsSold table:

+------------+---------------+-------+
| product_id | purchase_date | units |
+------------+---------------+-------+
| 1          | 2019-02-25    | 100   |
| 1          | 2019-03-01    | 15    |
| 2          | 2019-02-10    | 200   |
| 2          | 2019-03-22    | 30    |
+------------+---------------+-------+

Output:

+------------+---------------+
| product_id | average_price |
+------------+---------------+
| 1          | 6.96          |
| 2          | 16.96         |
+------------+---------------+